An ophthalmic device or apparatus (also called ophthalmologic device or ophthalmometer) is typically aligned to measure one eye, the right or the left eye, of an examinee and the measuring result is registered by the device. The device can, however, not usually distinguish between the right or the left eye and the registered result, thus, does not involve the information about which eye the result is concerned with.
Since ophthalmologic measurement results, such as those of tonometer measurements, and measurements related to the cornea, are different for the right and the left eye, it is important to know whether the measurement result relates to the right or the left eye of the examinee. For the time being there does not exist any ophthalmic device on the market that would be able to give this information reliably and automatically.
In prior art, some attempts have been made to solve this problem and some methods and means regarding eye related measurements being able to distinguish between the right eye and the left eye have been developed.
U.S. Pat. No. 6,056,404 presents an ophthalmic apparatus with a judging device for judging whether the eye is a right eye or a left eye using results detected by a photo-receiving device based on face boundaries. This document wants to solve the problem that arises when an examiner forgets to input data about whether it was the right eye or the left eye that was examined.
U.S. Pat. No. 5,861,937 presents an ophthalmic apparatus having a calculating unit for judging whether the aligned eye is the right eye or the left eye based on results detected by an optical system. A CCD camera is used for this purpose.
U.S. Pat. No. 5,561,482 presents an eye refractive power measuring apparatus with orientation dependent discrimination between right and left eyes. The apparatus performs a judging whether the eye to be examined is the right eye or the left eye. This solution uses infrared detection for sensing infrared rays emitted by the examinee's face. Infrared light emitted from examinees' faces is, however, quite weak to be detected and is not always possible to be discriminated from the environmental light.
EP patent 0 722 690 B1 relates to an ophthalmologic apparatus with discriminating means for discriminating whether the eye under examination being measured by said measuring device is the left eye or the right eye. Reflecting infrared light is used for that purpose. Even this system, however, is sensitive for errors caused by interfering infrared light from the environment, such as sunshine.